The Program Project Core was designed to ensure coherent support, communication, and synergy across the scientific Projects. The Core was specifically developed to achieve the following aims: (1) to manage human subject accrual and retention activities, which will include maintaining productive, cooperative relationships with the participants and the communities in which they reside;(2) to coordinate clinical assessments to characterize participants on relevant independent variables and potential confounds, including accumulation and distribution of demographic information, medical and substance use histories, psychiatric diagnoses (e.g., substance-related disorders), and laboratory data (e.g., viral load);(3) to provide the scientific Projects with data management support and guidance;(4) to supply statistical expertise and support to the scientific Projects;(5) to oversee and coordinate the activities of the various scientific Projects in an effort to ensure reliable exchange of information and collaborative interaction between Projects;and (6) to promote and ensure the Program Project's adherence to relevant federal, University, and IRB requirements. To accomplish these aims, the Core will consist of the following closely interacting Units, which will be overseen by the Principal Investigator: (1) Executive Unit;(2) Participant Accrual and Retention (PAR) Unit;(3) Clinical Assessment Assessment Unit;(4) Data Management and Information Systems Unit; and (5) Statistics Unit. In addition, the Core will coordinate the activities of critical internal and external working groups that support the aims of the Program Project, including the Council of Investigators, Director's Staff, Joint Research Review Committee, Confidentiality Committee, Participant's Advisory Board, Community Advisory Board, and Scientific Advisory Board. The Core is complemented by resources of the HIV Neurobehavioral Research Center (HNRC), which will enhance its economy and efficiency.